Magnetic printing arrangement



United States Patent [72] inventor Gerhard Ritzeri'eld,

l4 Schorlemer Allec, 33 Berlin (Dahlem),

Germany [21 Appl. No. 708,208 [22] Filed Feb. 26, 1968 [45] Patented Sept. 29, 1970 [32] Priority Feb. 28, 1967, Mar. 2, I967 [33] Germany [54] MAGNETIC PRINTING ARRANGEMENT 39 Claims, 1 1 Drawing Figs.

[52] U.S.Cl 101/216, 101/401.1,101/426,1l7/17.5,346/74 [51] lnt.Cl. 84115/00 [50] Field ot'Search IOI/(ESD), 401.l,368,395,426,216; 346/74; 117/175 56] References Cited UNITED STATES PATENTS 1,523,735 1/1925 VV ag ner.. 10l/395X 2,793,135 5/1957 Sims etal 346/74X 2,826,634 3/1958 Atkinson et al lO1/(ESD)UX 2,841,461 7/1958 Gleason ..1()1/(ESD)UX 2,857,290 10/1958 Bolton i0l/(ESD)UX 2,954,006 9/1960 Lawrence l0l/(ESD)UX 2,996,575 8/1961 Sims ..1()l/(ESD)UX 3,043,685 7/1962 Rosenthal 346/74X 3,052,564 9/1962 Kuleszo l0l/(ESD)UX 3,185,777 5/1965 Rheinfrank 346/74X 3,189,732 6/1965 Russell 346/74X 3,370,546 2/1968 Muller 101/91 Primary Examiner-Edgar S. Burr Attorney--Michael S. Striker ABSTRACT: A thin flexible master comprising a thin carrier sheet and magnetizable, character representing, mirror reversed printing portions, is placed on a rotary printing cylinder. The printing portions are magnetized to attract a colored iron toner powder and then brought into contact with a copy sheet to which the powder is transferred by a magnetic or electrostatic field. Finally, the copy sheet is heated so that the powder is baked into the same and represents characters or digits.

Patented Sept. 29, 1970 3,530 794 E FL. E

E E E I i N i l lnvenlar: 667562751 /c:C

Patented Sept. 29, 1970 3 ore Sheet Patented Sept. 29, 197 0 Sheet ie/d haw Late I f Patented Sept. 29, 1970 3,530,794

Sheet 4 rg Fig. 5

Patented Se t. 29, 1970 3,530,794

. Sheet, 5 018 Patented Sept. 29, 1970 Sheet F'atented Sept. 2 9, 1970 Sheet In van/0r:

Patented Sept. 29, 1970 3,530,794

she t 8 018 MAGNETIC PRINTING ARRANGEMENT BACKGROUND OF THE INVENTION Magnetic printing methods are known by which a picture is produced by means of magnets on a magnetizable drum. The picture carrying drums are bulky, and do not permit storing and reuse.

SUMMARY OF THE INVENTION It is one object of the invention to overcome this disadvantage of known magnetic printing methods, and to provide a printing arrangement in which a flexible thin master is used.

Another object of the invention is to attach character representing mirror reversed magnetizable printing portions to a thin flexible carrier sheet to form a master which can be mounted on a printing cylinder.

Another object of the invention is to provide a new method of making a master having magnetizable, character representing printing portions.

Another object of the invention is to provide a new method for placing a toner powder on magnetized printing portions of a master, and for transferring the powder from the printing portions to a copy sheet.

Another object of the invention is to provide a magnetic printing apparatus adapted for use with a master having magnetizable, character representing printing portions.

With these objects in view, a method according to the invention comprises the steps of placing one side of a flexible carrier sheet in contact with a layer of a magnetizable material, such as iron oxide which adheres to a base sheet; treating character representing portions of the other side of the carrier sheet, for example by the impact of type faces, so that mirror reversed, character representing portions of the layer adhere to the carrier sheet and form magnetizable printing portions on the same; and separating the carrier sheet from the base sheet so that the layer is divided into the printing portions which adhere to the carrier sheet and into a remainder adhering to the base sheet, which is discarded so that the carrier sheet and the magnetizable printing portions form a master.

Thereupon, the printing portions are magnetized, and a magnetizable toner powder, for example iron powder, is applied to the magnetized printing portions and adheres to the same. The powder is then transferred from the printing portions to a copy sheet, and the transferred powder is permanently attached to the copy sheet, for example by heating, so that the outlines of legible characters are formed on the copy sheet.

The transfer of the powder to the copy sheet may be accomplished by a strong magnetic field, or by electrostatic charges applied to the master and to the copy sheet, respectively. The copy sheets are preferably moistened with alcohol before the toner powder is transferred from the magnetized printing portions of the master to the copy sheet, and the moistening liquid may be selected so that the powder adheres to the copy sheet without further heating.

In a modified method of the invention, electrostatic charges of the same polarity are applied to the carrier sheet of the master and to the toner powder so that the same is repelled by the portion of the master located between the printing portions.

In another method of the invention, a conductive layer of low magnetic permeability is applied to the side of the carrier sheet remote from the side carrying the magnetizable printing portions. The conductive layer is complementary to the magnetizable printing portions, and covers the remainder of the carrier sheet. The conductive layer preferably includes tin, and when mounted on a metal printing cylinder, dissipates electrostatic charges applied to the master so that only the printing portions are electrostatically charged in addition to being magnetized whereby the application of the toner powder to the printing portion is facilitated and improved.

A magnetic printing apparatus according to one embodiment of the invention comprises a rotary printing cylinder having a peripheral surface on which one of the abovedescribed masters is placed. Magnetizing means magnetize the printing portions during rotation of the printing cylinder, and feeding means, preferably including a conveyor and a magnet, feed the toner powder to the magnetized printing portions to which it adheres. A counterpressure roller cooperates with the printing cylinder in a printing plane in which transfer means produce a force field for transferring the powder from the magnetized printing portions to the copy sheet. The transfer means are either a magnet in the printing drum or in the counterpressure roller, or the peripheral portion of the counter pressure roller is made magnetic. However, it is also possible to provide corona discharge devices for oppositely electrostatically charging the powder on the printing portion and the copy sheet whereby the transfer is accomplished. The copy sheet is then transported to an infrared heater, or to a high frequency generator producing heat in the copy sheet so that the powder is baked into the copy sheet.

It is advantageous to construct a printing cylinder with a tubular magnetizable wall supporting the master so that portions of the wall are also magnetized, particularly if the magnetizing means of the printing portions are located within the tubular wall of the printing cylinder. A corona discharge means may also be provided for charging the carrier sheet of the master with the same polarity as the feeding means of the toner powder, whereby the same cannot adhere to the carrier sheet portions between the magnetizable printing portions. In another modification, a corona discharge means applies a charge to the master which is only retained by the printing portions, and dissipated by conductive portions of the carrier sheet between the printing portions. In this manner, the transfer of the toner powder to the printing portions magnetized by a magnet in the interior of the hollow printing cylinder, is improved.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevation illustrating a blank pad for producing a master;

FIG. 2 is a fragmentary elevation illustrating a master and a discardable part produced of the blank of FIG. 1;

FIG. 3 is a fragmentary schematic side elevation, partially in section, illustrating a first embodiment of the invention using the master of FIG. 2;

FIG. 4 is a fragmentary schematic side elevation, partially in section, illustrating a printing machine according to a second embodiment of the invention and employing the master of FIG. 2;

FIG. 5 is a fragmentary schematic perspective view illustrating a direct current electromagnet used in the embodiment of FIG. 4;

FIG. 6 is a fragmentary schematic side elevation, partially in section, illustrating a printing machine in accordance with a third embodiment of the invention, employing a modified master;

FIG. 7 is a fragmentary view illustrating a detail of the printing machine of FIG. 6 on an enlarged scale;

FIG. 8 is a fragmentary side elevation illustrating a blank pad for producing a master according to another embodiment of the invention;

FIG. 9 is a fragmentary side elevation illustrating the master, and parts of the blank pad which can be discarded;

FIG. 10 is a fragmentary schematic side elevation, partially in section, illustrating a printing machine. according to another embodiment of the invention and using the master of FIG. 9; and

FIG. 1 1 is a fragmentary schematic side elevation, partially in section, and illustrating a printing machine according to another embodiment of the invention in which high voltage corona discharge means are used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrate the making of a master in accordance with one embodiment of the invention. A master sheet or carrier sheet 1 consisting of a non-magnetizable material, such as paper, is placed on top of and in contact with a layer 4a having about 40 parts by weight of iron oxide or ferrite which is adhesively attached to a waxed base sheet by an adhesive, preferably phenolic resin of about 3 parts by weight, which is either admixed to the iron oxide 4a, or forms a coat on the base sheet 5. The base sheet 5 is formed by coating a thin paper sheet with a waxy material of about 5 parts by weight. The combined sheets are placed in a typewriter, and imprints are made by a type bar 2 on the top face of master sheet 1 so that characters or digits 3 are formed on the top face of the master sheet 1.

Due to the impact of the type faces of type bar 2 on master sheet 1 and layer 4a, parts 4 having the configuration of the characters or digits 3 adhere to the bottom face of carrier sheet 1 when the same is separated from base sheet 5 to which the remaining portions 4b of layer 4a adhere.

FIG. 3 illustrates a rotary printing apparatus in which a master 1 as described with reference to FIG. 2, is used. A rotary printing drum 7 is mounted on a shaft 6 and is rotated by drive means including a one revolution clutch, not shown. A

clamping means 7a clamps the master sheet 1 so that the same is located on the cylindrical periphery of printing drum 7 with the iron oxide layer portions 4 facing outward. A hollow counterpressure roller 24 is mounted on a shaft 22 for rotation, and envelopes an axial row of electromagnets 23 having cores on which the inner'surface of the rotating counterpressure roller 24 slides. The outer surface of counterpressure roller 24 cooperates with the printing cylinder 7 and master 1 in a printing plane AB passing through the axes of printing drum 7 and counterpressure roller 24. Copy sheets 17 are supplied by means of a guide table 16 to a moistening device 21 for moistening the copy sheets with an alcoholic agent, whereupon the copy sheet is transported by rollersl8 and 19 over a guide 20 into'tlie bight between printing drum 7 and counterpressure roller 24, and in contact with the layer portions 4, and then guided by a guide means 26 into receiving container 27. A guide 9 facilitates the insertion of the master 1 into the clamping means 70.

When the machine is started, printing drum 7 turns in the direction of the arrow out of its illustrated initial position and performs one revolution.

An electromagnet 8 is mounted in the proximity of the leading part of master 1 and produces a magnetic field for magnetizing the magnetizable layer portions 4 which have the outlines of characters or digits. Following the magnetizing means 8, a container 10 is provided which can be vibrated by a vibrator 15 to loosen colored iron powder 11 in container 10 so that a rotary feeding means 13 which is supported by shaft 12 pushes iron powder 11 out of the container and throws the powder into the magnetic field of an applicator magnet 14 which prevents dropping of the iron powder and applies the powder to the master 1 so that it adheres to the magnetized character representing layer portions 4.

When text lines formed of magnetizable layer portions 4 pass through the printing plane AB, the iron powder 11 is transferred fromportions 4 to a copy sheet transported by counterpressure roller 24 due to the action of the transfer magnets 23 which act in the printing plane. Since the copy sheets are moist due to the action of the moistening means 21, the iron powder adheres to the copy sheets and is bonded to the copy sheet when the same slides on guide 26 and is heated by the infrared heating means 25.

In a modified arrangement, which will be explained hereinafter, the stationary transfer magnets 23 are omitted, and the counterpressure roller provided with a magnetic peripheral rubber cover. During the following revolution of printing drum 7, a new copy sheet 17 is supplied, the layer portions 4 are again magnetized by the field of electromagnet 8, covered with iron powder 11, and brought into contact with the next copy sheet for transferring the iron powder in the form of characters to the copy sheets.

As explained with reference to FIG. 1, the imprints 3 made by type bar 2 have the outlines of characters and digits and consequently the layer portions 4 are mirror reversed. Therefore, the imprints made on the copy sheet are legible.-

FIG. 4 illustrates a modified embodiment of the printing machine according to the invention. A printing drum 7 carries a master 1 into contact with copy sheets 17 supplied in moistened condition by transporting rollers 18 and 19 to the guide 20 and the printing plane between printing drum 7 and counterpressure roller 35. Feeding and applicator means 10, 13, 14 apply an iron powder 11 to the master 1 so that it adheres to the character representing magnetizable layer portions 4 which are magnetized by electromagnet 36 before the leading end of master 1 arrives in the region of applicator magnet 14. Iron powder 11 contains a dye or ink which makes it possible to use the imprinted copy sheet 17 as a master sheet.

After receiving the iron powder 11, the master 1 passes a high voltage corona discharge means 30, 31 whose positive field produces an electrostatic charge of the iron powder on the layer portions 4, while its negative field produces anegative electrostatic charge of the copy sheet passing guide 20 so that the iron powder 11 is transferred to the copy sheet when the same passes the printing plane AB. While the iron powder in the form of character outlines adheres to the copy sheet, the same is moved under the infrared heating means 25 which permanently bakes the dyed iron powder to the copy sheet. Since the powder is held on the copy sheet by the electrostatic charges, the moistening of the copy sheets by moistening means 21 may be omitted. On the other hand, if the moistening means 21 applies an adhesive to the copy sheet, the heating means 25 may be omitted.

FIG. 5 illustrates the applicator magnet 14 which includes an elongated core 32 and a winding 33. Core 32 has a length corresponding to the axial width of the master 1 and a rounded longitudinal edge which is placed in the proximity of the master so as to effect the uniform distribution of the iron powder 1 1. Winding 33 is energized by a direct current.

The modified printing machine illustrated in FIG. 6 uses a modified master la. As described with reference to FIG. 1, imprints are made on the master or carrier sheet 1 by type faces of type bars 2. A standard ink ribbon is used for making the imprints 3 of the master 1, but when master la is made, the type bars and type faces act on a ribbon containing iron oxide or ferrite so that the master la has magnetizable character representing imprints 41 in addition to the magnetizable layer portions 4 on the other side of the carrier sheet 1. Imprints 41 register with the layer portions 4, and are legible, while layer portions 4 are mirror reversed. I

Master la is attached to the periphery of a hollow printing drum which has a tubular wall 40 consisting of a magnetizable material, such as iron. Iron powder 11, which is enriched with wax or a synthetic material is located in a container 10 and transported by an endless conveyor band 44 into the proximity of the master la. Conveyer band 44 is driven by rollers on shafts 42 and 43, and receives an electrostatic charge by high voltage corona discharge means 45. The character representing layer portions 4, the imprinted characters 41, and the surface of printing drum 40 are magnetized by the field of electromagnet 8 so that the powder on the conveyor 44 is strongly attracted and applied to the layer portions 4 to which it adheres.

As best seen in FIG. 7, the distance between the iron powder ll'on conveyor band 44, and the iron oxide layer portions 4 is selected so that the iron powder 11 is transferred by the magnetic field of the magnetized character representing layer portions 4. However, the distance should not be so small that iron powder 11 is attracted by the magnetized surface of printing cylinder 40 to the portions of the master sheet between the character representing layer portions 4.

The master is further transported by the rotating printing cylinder 40 into the printing plane A-B so that the lines of character representing layer portions 4 successively pass the field of a stationary transfer magnet 46 which de-magnetizes the wall of printing cylinder 40, the character representing portions 41, and the character representing portions 4 so that the iron powder is transferred to the moistened copy sheet 17 to which it adheres until baked into the same by the infrared heating means 25. Transporting rollers 18 and 19, and counterpressure roller 35 transport the copy sheets successively along guide 20 and guide 26 into the receptacle 27.

FIGS. 8 and 9 illustrate the making of a master in accordance with another embodiment of the invention. The carrier sheet 1 is provided with a layer 50 consisting of tin in a thickness of between 5 and microns. A wax layer or layer consisting of a synthetic material 51, preferably polyvinyl chloride in a thickness of between and 30 microns, carried by a paper base sheet 52, is placed on top of and in contact with the tin layer'50. An iron oxide layer or ferrite powder layer 54 on a paper base sheet 53 is placed below and in contact with the carrier sheet 1.

The blank pad 1, 5054 is placed in a typewriter and the type bars 2 are operated to impress the base sheet 52. Due to the impacts of the type faces, portions 50a of layer 50 having the outlines of characters adhere to the wax layer 51 while the remainder of tin layer 50 remains on carrier sheet 1 when sheets 1 and 52 are separated.

Also due to the impacts of the type faces, character representing layer portions 54a adhere to the carrier sheet 1, while the remainder of the iron oxide layer 54 adheres to the paper sheet 53 when the same is separated from the carrier sheet 1.

The master lb consists of the carrier sheet 1, of magnetizable, character representing mirror reversed magnetizable layer portions 54a on one side, and with the remainder of the tin layer 50a on the other side. The remainder of tin layer 50 is the complement of the character representing magnetizable layer portions 540 which have the outline of mirror reversed characters. The area of carrier sheet 1 is consequently covered on one or the other side by layer portions 50 or 54a. Layer portions 50 consist of a non-magnetizable but highly conductive and electrically chargeable material, for example tin, and layer portions 54a consist of a magnetizable material, such as iron oxide or ferrite.

In a modified method of making the master lb, wax is admixed to the tin layer 50, the wax layer 51 is omitted, and paper sheet 52 directly applied to the tin and wax layer. Upon separation of sheets 1 and 52,.layer portions 50 and 50a, as described with reference to FIG. 9, are formed.

In both methods of making master lb, an adhesive is either contained in the iron oxide or ferrite layer 54, or is applied as a coat to carrier sheet 1 and paper sheet 53 to assure separation of layer portions 54a from the remaining magnetizable layer 54.

FIG. 10 illustrates a printing machine in which a master lb as shown in FIG. 9 is used. The printing cylinder 40 is hollow and has a cylindrical peripheral wall consisting of a magnetizable material. The printing cylinder, and the master lb thereon, cooperate with a counterpresshre rolEr ilsa toimp rint copy sheets 17 moistened by the m'oistening devigell an l transported by transporting rollers 18 and 19 over a guide 20 to the printing plane A- B from where the copy sheet passes over a guide 26 into a receptacle 27. The master sheet is supplied over a guide 9 to the clamping mea 71 A' stationary shaft 6 supports printing cylinder 46 forrotation in the direction of the arrow, printing cylinder 40 being driven by drive means over a one revolution clutch, not shown. Stationary magnets 46 and 58 are secured to shaft 6 and have cores located adjacent the inner surface ofthe peripheral wall of the printing cylinder 40 at angularly spaced points.

Master lb is attached to the periphery of the printing cylinder in a position in which the character representing mirror reverse magnetizable layer portions 540 face outward, while the complementary non-magnetizable conductive layer 50 faces inward.

At the beginning of a revolution of the printing cylinder, the leading portion of master lb passes the stationary magnet 58 whose field penetrates the magnetizable wall of the printing cylinder and a magnetizable layer portion 54 so that the same attracts iron powder 11 transported into a hopper 61 by an endless conveyor 60 disposed in a container 59 which is vibrated by a vibrator 15 in order to maintain the iron powder 1 1 in a loose condition.

Before the master enters the region between applicator magnet 58 and hopper 61, it passes through a high voltage corona discharge means 55 which produces a negative charge in the magnetizable layer portions 54, whereas the remainder of the carrier sheet 1 cannot be electrostatically charged since the conductive layer 50 dissipates the charge to the mass of the printing cylinder. The negative electrostatic charge improves the transfer of the colored iron powder 11 over the air gap to layer portions 54, and since the same are magnetized by applicator magnet 58, the powder is held on the layer portion 54 while the master lb is transported into the region of the printing plane A-B where it is brought into contact with a copy sheet 17. The magnet 46 de-magnetizes the layer portions 54 and the iron powder thereon, which is attracted by a tubular cover 35a of the counter pressure roller 35, since cover 35a consists of rubber with iron powder embedded therein, and is magnetized by a magnet 57. The colored iron powder transferred to a copy sheet 17 has the outlines of characters or digits, and when the copy sheet is further transported over guide 26, it is subjected to the radiation of a high frequency radiator 62, or to heat produced by heating means, so that the iron powder is baked into the copy sheet which is deposited in the receptacle 27.

The embodiment illustrated in FIG. 11 is a modification of the embodiment of FIG. 6, and uses a master 1 having ink imprints 3, as described with reference to FIG. 2, or a master la having magnetizable imprints 41, as described with reference to FIG. 6.

As in the embodiment of FIG. 10, the printing cylinder cooperates with a counterpressure roller having a tubular magnetizable cover 350 which is continuously magnetized by an electromagnet 57.

During a revolution of the printing cylinder, the leading portions of the master first pass through the magnetic field of an electromagnet 8 so that the character representing mirror reversed magnetizable layer portions 4 are magnetized. Directly thereafter, a high voltage charging means 54 charges the remainder of the master sheet with a negative charge.

The iron powder 11 is transported into the region of the master by an endless conveyor 44 which is provided with a negative charge by the high voltage charging means 56. The charged iron powder is repelled by the sheet portions of master sheet 1 which are electrostatically charged, and attracted by the magnetized layer portions 4 so that a clear separation is maintained. The iron powder is transferred from the master to the surface of a copy sheet 17 in the printing plane A-B since the iron powder is attracted by the magnetic tubular cover 35a of the counterpressure roller. The moisture of copy sheet 17 causes the character outlines consisting of iron powder to adhere to the copy sheet until it is baked into the same by the infrared heating means 25.

It is advantageous to assure full contact between the master sheet and the peripheral surface of the printing cylinder, by electrostatically charging the printing cylinder before the master is attached. In this modification of the invention, at least the peripheral wall of the printing cylinder consists of a non-conductive material which is adapted to be electrostatically charged.

The above-described printing machines can be adapted for selective printing by mounting the counterpressure roller movable between a position spaced from the printing cylinder, and the illustrated position cooperating with the same. When selected portions of the master pass the printing plane, the counterpressure roller is operative so that the respective portions are printed, but when undesired portions of the printing form pass the printing plane, the counterpressure roller is moved away so that no-imprint is made on the copy sheet. This arrangement is known, but can be advantageously applied to the printing machines according to the present invention.

It is possible to omit the heating means 25 or 62, and to fix the powder imprints on the copy sheet only by the fixing agent, containing alcohol, applied by the moistening means 21.

The magnetizing means 8 may have a core of soft iron, and be excited by a current of high frequency, for example 500 Hertz. However, a direct current magnet can also be used, particularly in the embodiment illustrated in FIG. 5.

The toner powder is made magnetizable and electrostatically chargeable in the embodiment of FIG. 4 so that it can be applied by magnet 14 to the magnetizable printing portions 4, and transferred to a copy sheet having an opposite electrostatic charge.

In the embodiment of FIG. 6 in which the printing cylinder has a tubular wall consisting of a magnetizable material of high remanence, the same is magnetized by the magnetizing means 8. The amount of magnetization of the tubular wall, and of the magnetizable printing portions 4 is selected so that the toner powder can move from conveyor 44 across the gap onto the already magnetized printing portions 4, but cannot move across the greater gap to the carrier sheet of the master In at points intermediate the printing portions 4. The distance from the feeding means of the toner powder to the surface of the carrier sheet of the master is preferably twice as great as the distance of the same to the outer printing faces of the printing portions 4. The effect of the magnetizable tubular wall of printing cylinder 46 is improved when inner portions 41, consisting of a magnetizable material, register with the magnetizable printing portions 4, as shown in FIG. 6. The feeding means of the toner powder can be spaced a very small distance, for example approximately 0.2 mm to 0.3 mm from the peripheral surface of the tubular wall of the printing cylinder and from the master.

In the embodiment of FIG. 3, the toner powder is removed from the feeding roller 13 by an electromagnet 14 which preferably has a ferrite core extending in axial direction along the printing cylinder and the master.

The tubular cover 35 of the counterpressure roller is preferably made of rubber with iron powder embedded, and may be permanently magnetized. However, in the embodiment of FIGS. and 11, a magnet 57 continuously magnetizes the tubular cover of the counterpressure roller during rotation of the same.

In the embodiment of FIG. 11, the master 1 is electrostatically charged by a corona discharge device 55 so that the portions of the master intermediate the magnetizable printing portions 4 repel the toner powder which is charged with the same polarity by another corona discharge device.

In the embodiment of FIG. 10, the carrier sheet 1 of the master is made of a material of high permeability, for example paper, while the inner portions 50 have substantially lower permeability. Since the magnetizable printing portions 54 and the inner portions 50 of low permeability are complementary, the portions of the master where the printing portions 54 are located are more permeable than the complementary remainder of the master sheet. Since the tubular wall of printing cylinder 40 is also magnetizable and highly permeable, the

applicator magnet 58 can be disposed in the interior of the so that only the printing portions 54 are covered with the toner powder which adheres to the same. Transfer magnet 46 de-magnetizes the master and transfers the powder to the copy sheet.

The tin layer 50 described with reference to FIGS. 8 and 9 may be combined with the wax layer 51 in a wax layer in which powdered tin is embedded, but it is also possible to attach a thin tin foil to the base sheet 52 by an adhesive whose adhesive force, after treatment by the impact of the type bar 2, is greater than the adhesive force which holds the tin foil on the carrier sheet 1.

It is possible to provide magnetizing means which combine the inner magnet 58 of FIG. 10, with the outer magnet 8 of FIGS. 3, 6 and 11. In this event, the polarity of the two magnets is opposite.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of magnetic printing arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in a method and apparatus for magnetic printing with a flexible master sheet having magnetizable printing portions and being mounted on a rotary printing cylinder, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

I claim:

1. Magnetic printing method comprising placing one side of a flexible carrier sheet in contact with a layer of a magnetizable material adhering to a base sheet; treating character representing portions of the other side of said carrier sheet so that mirror reversed, character representing portions of said layer adhere to said one side of said carrier sheet and form magnetizable printing portions on the same; separating said carrier sheet from said base sheet so that said layer is divided into said printing portions which adhere to said carrier sheet, and into a remainder adhering said base sheet; discarding said base sheet so that said carrier sheet and printing portions form a master; magnetizing said printing portions; applying a magnetizable toner powder to said magnetized printing portions so that said powder adheres to the same; transferring said powder from said printing portions to a copy sheet so that the transferred powder forms the outlines of legible characters on the same; and permanently attaching said transferred powder to said copy sheet.

2. Magnetic printing method as claimed inclaim 1 wherein a magnetic field is applied to said powder for transferring the same from said magnetized printing portions to said copy sheet, said magnetic field being selected to demagnetize said magnetized printing portions.

3. Magnetic printing method as claimed in claim 1 wherein said printing portions are magnetized by a magnetic field produced by an electromagnet excited at a current frequency of approximately 500 l-Iertz.

4. Magnetic printing method as claimed in claim 1 wherein said printing portions are magnetized by a magnetic field of an electromagnet excited by direct current.

5. Magnetic printing method as claimed in claim 1 wherein opposite electrostatic charges are applied to said powder on said printing portions and to said copysheet, respectively, for transferring said powder from said printing portions to said copy sheet.

6. Magnetic printing method as claimed in claim 1 comprising the steps of charging a printing cylinder with an electrostatic charge; and attaching said master to said printing cylinder so that said charge holds said carrier sheet in contact with the surface of said printing cylinder.

7. Magnetic printing method as claimed in claim 1 comprising the step of attaching said master to a rotary printing cylinder having a peripheral magnetizable wall magnetized by the magnetic field by which said printing portions are magnetized, and being spaced from the source of said powder a greater distance than said printing portions so that said powder is applied to said printing portions and not to the remainder of said master.

8. Magnetic printing method as claimed in claim 1 wherein said treating of character representing portions on said other side of said carrier sheet includes impressing character representing type faces on said other side of said carrier sheet.

9. Magnetic printing method as claimed in claim 8 wherein said character representing portions are impressed by said type faces through an inked ribbon.

10. Magnetic printing method as claimed in claim 8 wherein said character representing portions are impressed by said type faces through a ribbon containing a magnetizable substance so that character representing legible magnetizable deposits are produced on said one side of said carrier sheet registering with said mirror reversed magnetizable printing portions.

11. Magnetic printing method as claimed in claim 1 wherein said magnetizable material is iron oxide; and wherein said toner powder is an iron powder.

12. Magnetic printing method as claimed in claim 1 wherein said layer of a magnetizable material consists of magnetizable ferrous powder embedded in a waxy layer.

13. Magnetic printing method as claimed in claim 1 wherein said carrier sheet consists of a non-magnetizable electrostatically chargeable material; and comprising applying electrostatic charges of the same polarity to said carrier sheet and to said toner powder so that the same is repelled by the portion of said master located between said magnetizable printing portions.

14. Magnetic printing method as claimed in claim 1 wherein said treating of said other side of said carrier sheet includes placing a conductive layer of low magnetic permeability of another base sheet in contact with said other side; adhesively attaching said conductive layer to said other side of said carrier sheet; forming characters on the side of said other base sheet remote from said conductive layer; and separating said other base sheet from said carrier sheet so that character representing portions of said conductive layer adhere to and are removed with said other base sheet, and the complementary remainder of said conductive layer adheres to said other side of said carrier sheet so that said printing portions formed on said one side of said carrier sheet are complementary to said remainder of said conductive layer of low magnetic permeability so that only said magnetizable printing portions are magnetized by said magnetizing means and attract said toner powder.

15. Magnetic printing method as claimed in claim 14 wherein said characters are formed on said other base sheet by impressing character representing type faces.

16. Magnetic printing method as claimed in claim 14 wherein said conductive non-magnetizable layer includes wax and powdered tin.

17. Magnetic printing method as claimed in claim 14 comprising the step of placing said master on a conductive printing cylinder so that said complementary remainder of said conductive layer is in contact with the same and said magnetizable printing portions face outward; applying an electrostatic charge to the outside of said master so that said printing portions are charged while a charge applied to the remainder of said master is dissipated through said conductive portions and said printing cylinder so that said toner powder is attracted by the electrostatic charge of said printing portions in addition to the magnetic attraction produced by said magnetized printing portions.

18. Magnetic printing arrangement as claimed in claim 1 including moistening said copy sheet before transferring said powder to said copy sheet so that said powder is attached to said copy sheet; and wherein said permanently attaching of said powder to said copy sheet includes heating said copy sheet and the powder thereon.

19. Magnetic printing method as claimed in claim 1 wherein said carrier sheet includes a paper sheet and a thin tin foil attached to said other side of said paper sheet.

20. Magnetic printing method as claimed in claim 19 wherein said treating includes placing another base sheet having an adhesive layer on said carrier sheet with said adhesive layer adhering to said tin foil; impressing type faces representing characters on said other base sheet so that character representing portions of said tin foil adhere to said adhesive layer; and separating said other base sheet from said carrier sheet so that character representing portions of said tin foil are removed with said other base sheet, and the complementary remainder of said tin foil adheres to said carrier sheet so that said printing portions on said one side of said carrier sheet are complementary to said remainder of said tin foil on said other side of said carrier sheet.

21. Magnetic printing apparatus comprising, in combination, a rotary printing cylinder; a holder on said printing cylinder; a master having on a non-magnetizable surface magrietizable printing portions in the form of mirror reversed characters and being held by said holder on the peripheral surface of said printing cylinder; magnetizing means for magnetizing only said printing portions during rotation of said printing cylinder; feeding means for feeding a magnetizable powder to said magnetized printing portions so that said powder adheres to the same; counter-pressure roller means cooperating with said printing cylinder in a printing plane, said magnetizing means, feeding means and counter-pressure roller means being successively passed by said master during a revolution of said printing cylinder; transporting means for transporting a copy sheet to said printing plane and into contact with said printing portions; transfer means producing in said printing plane a force field acting on the powder magnetically adhering to said magnetized printing portions so that said powder is transferred directly to said copy sheet; and means for permanently attaching the transferred powder to said copy sheet so that legible characters are formed on the same by the transferred powder.

22. Magnetic printing apparatus as claimed in claim 21 wherein said feeding means include an applicator magnet, and means for conveying said powder to said applicator magnet, said applicator magnet being an electromagnet having a core spaced a distance of approximately 0.25 mm from said master and said peripheral surface of said printing cylinder.

23. Magnetic printing apparatus as claimed in claim 21 wherein said magnetizing means include an electromagnet having a core located closely adjacent said master and said peripheral surface.

24. Magnetic printing apparatus as claimed in claim 21 wherein said counterpressure roller means includes a rotary tubular roller; and wherein said transfer means include a stationary electromagnetic means located in the interior of said tubular roller and having core means aligned with said printing plane and adjacent the inner surface of said tubular roller.

25. Magnetic printing apparatus as claimed in claim 21 wherein said printing cylinder has a magnetizable tubular wall having said peripheral surface on the outside; and wherein said transfer means include a stationary electromagnet in the interior of said tubular wall having core means aligned with said printing plane and located adjacent the inner surface of said tubular wall and producing a magnetic field opposite to the magnetic field produced by said magnetized printing portions.

26. Magnetic printing apparatus as claimed in claim 24 wherein said magnetizing means include another electromagnetic means located in said interior of said tubular wall angularly spaced from said stationary electromagnet.

27. Magnetic printing apparatus as claimed in claim 21 wherein said counterpressure roller means includes a rotary roller and a tubular magnetizable cover about the periphery of said rotary roller and cooperating with said printing cylinder; and wherein said transfer means include a stationary magnet for magnetizing said tubular cover during rotation of the same.

28. Magnetic printing apparatus as claimed in claim 21 wherein said transfer means include electrostatic charging means for producing opposite charges in said copy sheet and in said master so that said powder is transferred from said magnetized printing portions to said copy sheet.

29. Magnetic printing apparatus as claimed in claim 21 wherein said printing cylinder has a tubular magnetizable wall havingsaid peripheral surface on the outside; wherein said master has said magnetizable printing portions on the outside and magnetizable inner portions on the inside in contact with said peripheral surface and exactly registering with said printing portions; wherein said magnetizing means include electromagnetic means for magnetizing said printing portions, said inner portions, and said tubular wall; wherein said transfer means include a stationary magnet in the interior of said tubular wall having a core adjacent the inner surface of the latter and producing a magnetic field for demagnetizing said printing portions, said magnetizable inner portions, and said tubular wall in the region of said printing plane.

30. Magnetic printing apparatus as claimed in claim 28 comprisinga stationary shaft supporting said printing cylinder for rotation; and wherein said stationary magnet is secured to said shaft. I

31. Magnetic printing apparatus as claimed in claim 21 wherein said feeding means includes a container for said toner powder, a vibrator for vibrating said container and for loosening said powder, and means for conveying the powder from said container into the proximity of said master and printing cylinder.

32. Magnetic printing apparatus as claimed in claim 31 wherein said means for conveying includes an endless conveyor band; and comprising corona discharge means for electrostatically charging said endless conveyor band.

33. Magnetic printing apparatus as claimed in claim 21 wherein said means for permanently attaching said powder to a copy sheet include a high frequency wave radiator.

34. Magnetic printing apparatus as claimed in claim 21 wherein said master includes a carrier sheet having said magnetizable portions thereon; wherein said feeding means are spaced from said printing portions approximately half the distance said feeding means are spaced from said carrier sheet; and wherein said magnetizing means are selected to magnetize said printing portions to such an extent that said powder fed by said feeding means is attracted by said printing portions but not attracted to said carrier sheet.

35. Magnetic printing apparatus comprising in combination, a rotary printing cylinder; a holder on said printing cylinder; a master having magnetizable printing portions in the form of mirror reversed characters and being held by said holder on the peripheral surface of said printing cylinder; magnetizing means for magnetizing said printing portions during rotation of said printing cylinder; feeding means for feeding a magnetizable powder to said magnetized printing portions so that said powder adheres to the same; counterpressure roller into contact with said printing portions; transfer means producing in said printing plane a force field acting on the powder magpetically adhering to said magnetized printing portions so at said powder is transferred to said copy sheet; and means for permanently attaching the transferred powder to said copy sheet so that legible characters are formed on the same by the transferred powder.

36. Magnetic printing apparatus as claimed in claim 32 wherein said magnetizing means include magnetic means in the interior of said printing cylinder; and wherein said corona discharge device is located outward of said printing cylinder and said printing form.

37. Magnetic printing apparatus comprising in combination, a rotary printing cylinder having a tubular magnetically permeable wall with a peripheral surface; a holder on said printing cylinder; a master having magnetizable printing portions in the form of mirror reversed characters, and being held by said holder on the peripheral surface of said tubular magnetically permeable wall; said master sheet having said magnetizable printing portions on the outside, and identical magnetizable inner portions on the inside registering with said printing portions and abutting said peripheral surface so that the field of said magnetizing means permeates and magnetizes said printing portions, said inner portions, and said tubular wall, magnetizing means for magnetizing said printing portions during rotation of said printing cylinder; feeding means for feeding a magnetizable powder to said magnetized printing portions so that said powder adheres to the same; counterpressure roller means cooperating with said printing cylinder in a printing plane; said magnetizing means, feeding means and counterpressure roller means being successively passed by said master during a revolution of said printing cylinder; transporting means for transporting a copy sheet to said printing plane and into contact with said printing portions; transfer means producing in said printing plane a force field acting on the powder magnetically adhering to said magnetized printing portions so that said powder is transferred to said copy sheet; and means for permanently attaching the transferred powder to said copy sheet so that legible characters are formed on the same by the transferred powder.

38. Magnetic printing apparatus comprising, in combination, a rotary printing cylinder having a magnetizable tubular wall; a holder on said printing cylinder; a master having on the outside magnetizable printing portions in the form of mirror reversed characters and complementary portions of low magnetic permeability on the inside, said master being held by said holder on the peripheral surface of said tubular wall; magnetizing means located outside of said rotary printing cylinder for magnetizing said printing portions during rotation'bf said printing cylinder and including an electromagnetic means located in the interior of said tubular wall; feeding means for feeding a magnetizable powder to said magnetized printing portions so that said powder adheres to the same; counterin a printing plane, said magnetizing means, feeding means and counter-pressure roller means being successively passed by said master during a revolution of said printing cylinder; transporting means for transporting a copy sheet to said printing plane and into contact with said printing portions; transfer means producing in said printing plane a force field acting on the powder magnetically adhering to said magnetized printing portions so that said powder is transferred to said copy sheet; and means for permanently attaching the transferred powder to said copy sheet so that legible characters are formed on the same by the transferred powder.

39. Magnetic printing apparatus as claimed in claim 38 wherein said transfer means include a magnet in said interior of said tubular wall, and means for magnetizing at least the peripheral surface of said counterpressure roller. 

